Don't turn off anti-aliasing for image backgrounds unless the device scale factor is large enough.

Source/core/paint/ImagePainter.cpp

Index: Source/core/paint/ImagePainter.cpp
diff --git a/Source/core/paint/ImagePainter.cpp b/Source/core/paint/ImagePainter.cpp
index 04ebee1f5e6d0eee700066c2648c8239f05b760e..e4760e338f10fd54c9401a89a3bf9ed3e5dc6a30 100644
--- a/Source/core/paint/ImagePainter.cpp
+++ b/Source/core/paint/ImagePainter.cpp
@@ -200,16 +200,20 @@ void ImagePainter::paintIntoRect(GraphicsContext* context, const LayoutRect& rec
     InspectorInstrumentation::didPaintImage(&m_renderImage);
 }
 
+float deviceScaleFactor(LocalFrame*);

[jbroman, 2014/11/14 19:13:47]

drive-by: Why not include Page.h? Declaring extern functions within source files
seems odd.

[enne (OOO), 2014/11/14 19:15:59]

What is this, an extern? Maybe you should just add the right include?

[chrishtr, 2014/11/14 19:16:09]

Done.

+
 void ImagePainter::paintBoxDecorationBackground(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     // Don't anti-alias the background of an image. See crbug.com/423834 for the reason why.
     // However, don't turn off anti-aliasing for subclasses such as video.
-    bool shouldAntialias = !m_renderImage.isRenderImage();
+    // An additional mega-hack here is to turn off anti-aliasing only for situations with a large device scale factor
+    // The referenced bug gives more details about a device with a scale factor greater than 3.4).
+    bool shouldAntialias = !m_renderImage.isRenderImage() || blink::deviceScaleFactor(m_renderImage.frame()) < 3.4;
 
     bool oldShouldAntialias = paintInfo.context->shouldAntialias();
-
     paintInfo.context->setShouldAntialias(shouldAntialias);
     BoxPainter(m_renderImage).paintBoxDecorationBackground(paintInfo, paintOffset);
+
     paintInfo.context->setShouldAntialias(oldShouldAntialias);
 }